From the press release from Fiio, I understand that the new ESS unit and the old AKM are functionally identical, gain levels are the same (three), and SINAD should be a bit higher, supossedly what afected SINAD was the volume control chip (SINAD was higher at lower voltage output levels, so it was a non issue from an audibility point of view).
What I would have liked them to introduce was a fixed RCA output, but it hasn't happened, and price has increased, let's wait for reviews, but I don't think that from the user's point of view this is a significant improvement (if it is at all).